Calcium hypochlorite can exist as the anhydrous material and as a dihydrate. The strength of calcium hypochlorite products is often expressed in terms
of percent available chlorine (% av Cl2). The dihydrate is produced on a large scale and marketed as a 65-70% av Cl2 product. The commercial product
is a complex mixture containing variable amounts of related salts, such as sodium chloride, calcium chloride, calcium chlorate, calcium hydroxide,
calcium carbonate and other impurities. Calcium hypochlorite is also sold with 75-80% or 50% av Cl2, 35-37% av Cl2 (bleaching powder) and 33-35%
(tropical bleach). Historically, calcium hypochlorite sometimes contained impurities such as magnesium hypochlorite, which made the product
dangerously reactive.
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